1. Field of the Invention
This invention relates to filament reinforced composite articles.
2. Description of the Prior Art
The use of metal matrix filament reinforced composite tapes for the manufacturer of composite articles is well known in the art. For example, boron/aluminum and silicon carbide coated boron/aluminum composites are receiving widespread interest in the aerospace industry because of their excellent mechanical properties and low weight. These boron/aluminum composites offer a number of advantages over the well known boron filament/resin matrix composites in view of their isotropy of elastic and strength properties. Consequently, in many structural applications where multi-directional loads are present, boron/aluminum can offer advantages over resin matrix composites. However, a series disadvantage of prior art filament/metal matrix fabrication techniques is that the final molding operation may take four hours or more. The reason for this is that the metal matrix material is consolidated within the die at the final molding operation and/or the individual plies are diffusion bonded together during the final molding operation. In either event pressures on the order of several thousand pounds per square inch and temperatures on the order of about 800.degree.F and higher are required for optimum diffusion bonding of the plies and consolidation of the metal matrix. The equipment required for this process is expensive particularly in view of the high pressures required; furthermore, this equipment is not readily available to smaller manufacturing firms and is frequently impractical for fabricating large articles. These considerations and the fact that the bonding operation for each part requires several hours reduces the cost effectiveness of the material making it impractical to use for many applications. On the other hand, filament reinforced resin matrix composites can be consolidated at relatively low temperatures and pressures.
U.S. Pat. No. 3,606,667 to Kreider describes one technique for making unconsolidated filament reinforced metal matrix tapes and also discusses simultaneously diffusion bonding and consolidating several layers of these tapes at high pressures and temperatures to form a composite article. Kreider et al U.S. Pat. 3,615,277 also describes a process for fabricating an unconsolidated filament reinforced metal matrix tape, a plurality of these tapes being braze bonded to each other and consolidated at low pressures but at diffusion bonding temperatures.